Abstract:

4-nonylphenol (NP), a surfactant degradation product, is an unregulated,
ubiquitous aquatic contaminant and endocrine disruptor, for which aquatic life
criteria are currently under development by U.S. EPA. The effects of NP on
estuarine amphipods and chinook salmon fry were investigated, and this
dissertation reports research into the impacts of NP bioaccumulation on the
amphipods and resultant endocrine disruption of their juvenile salmon predators.
Sensitivity to, and bioaccumulation of, NP by benthic amphipods were quantified.
Factors affecting the bioavailability of NP to three species of amphipod
(Eohaustorius estuarius, Grandidierella japonica, and Corophium salmonis) were
determined in contaminated sediments. Standard bioassay techniques were
modified to determine toxicity and bioaccumulation, with varying amounts and
differing nutritional qualities of sedimentary organic carbon. ¹⁴C-Ring-labeled NP
was used as a tracer in the experiments to quantify amphipod exposures. NP was
acutely toxic to Eohaustorius estuarius from aqueous exposures, mean (+/-SD)
LC50=227 μg/L +/- 56, 1 h mean reburial EC50=138 +/- 36. The predicted LC50
for NP (202 μg/L) from an amphipod-derived structure-activity relationship was
not significantly different (p>0.05) from our empirically derived LC50 (227 μg/L).
All three amphipod species accumulated significant NP body burdens.
Accumulation was inversely proportional to the total amount of organic carbon, but
it did not differ between types of organic matter. Calculated accumulation factors
indicated that amphipods could be an important and previously unrecognized
source of NP to higher trophic levels. Plasma vitellogenin (Vtg) was quantified in
juvenile chinook salmon following dietary exposure to NP contaminated
amphipods and aqueous exposure to multiple NP concentrations. Fry that had fed
upon contaminated amphipods did not have significantly greater Vtg levels than
controls; however, Vtg was detected in 30 percent of fry. NP aqueous
concentrations at 60 and 240 μg/L significantly induced Vtg in fry following 5 d
exposures. The 240 μg/L aquatic NP treatment fry had comparable levels of Vtg to
the positive control treatment in which fry were injected 17B-estradiol. These
results indicate that amphipods are potential vectors of sediment NP to higher
trophic levels within the water column, including juvenile chinook salmon.